Mechanism to mitigate color breakup artifacts in field sequential color display systems

• US 8,115,776 B2
• Filed: 08/01/2006
• Issued: 02/14/2012
• Est. Priority Date: 08/02/2005
• Status: Expired due to Fees

• Current Assignee: Rambus Delaware
• Original Assignee: Rambus Inc.
• Inventors: Selbrede, Martin G., Zemen, Rick
• Primary Examiner(s): Sajous, Wesner
• Application Number:
  US11/913,232
• Publication Number:
  US 20080192065A1
• Time in Patent Office: 2,023 Days
• Field of Search: 345 88- 90, 345/426, 345/428, 345/581, 345/589, 345/619, 345/204, 345/207, 345690-691, 345213-214, 345/48, 345/77, 345 83- 84, 348 68- 70, 348268-269, 348500-503, 348/557, 348/742, 348/759, 349/1, 349 61- 62, 349104-106, 349/25, 349/31
• US Class Current: 345/589
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0266 Reduction of sub-frame artefacts
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3473 based on light coupled out of a light guide, e.g. due to scattering, by contracting the light guide with external means

Abstract

A mechanism for mitigating undesired color image breakup artifacts arising in display systems that exploit the principle of field sequential color generation. By suitably reducing the time interval during which image information strikes the moving retina, such that the differential position for the respective red, green, and blue components of the image falling upon the moving retina does not exceed the diameter of a retinal cone or rod, the cause of the breakup is negated and the image becomes unitary as expected: the eye sees the image as if all the components arrived at the same time. The truncation of light emission into shorter time frames necessitates a compensatory increase in imaging light intensity, such that the net amount of photonic flux striking the retina, averaged over time, remains unchanged. The mechanism can be applied to systems with discrete red, green, and blue sources as well as to color-wheel-based systems.

Claims

1. A system for displaying a respective image in response to each frame of a field-sequential video signal, the system comprising:

light sources of different primary colors;

a light guide having a light input edge for receiving light of the different primary colors from the light sources and propagating the light in the light guide by total internal reflection; and

an array of pixels that are opened and closed by a movable member that deforms under application of an electric field to frustrate the total internal reflection of propagated light in the light guide at defined locations on the light guide according to a predetermined shuttering sequence to output light of the different primary colors from the light guide consecutively in a time of less than 4 milliseconds during the frame of the video signal, and to output no light during the remainder of the frame,

the pixels being operable to modulate the light of each primary color output from the light guide in at least one of intensity and pulse width.

2. The system of claim 1, wherein the system is a projection-based field sequential color-based display system.

3. The system of claim 1, wherein the system is a direct-view field sequential color-based display system.

4. The system of claim 1 wherein the pixels are operable to generate gray scale.

5. The system of claim 1, wherein the gray scale generation comprises amplitude intensity modulation.

6. The system of claim 4, wherein the gray scale generation comprises amplitude intensity modulation.

7. The system of claim 1, wherein the light of the different primary colors is cycled synchronously at fixed intervals regardless of program content.

8. The system of claim 1, wherein the light sources that generate the different primary colors are discrete light sources that are independently controlled.

9. The system of claim 8, wherein the light of the different primary colors is cycled asynchronously during the frame according to program content.

10. The system of claim 1, wherein an intensity of the light of the different primary colors is increased by a ratio of 1/n, wherein n is equal to a number of different primary colors output by the light guide.

11. A method for displaying a respective image in response to each frame of a field-sequential video signal, the method comprising:

opening and closing an array of pixels by a movable member that deforms under application of an electric field to frustrate total internal reflection of propagated light of different primary colors in a light guide at defined locations on the light guide according to a predetermined shuttering sequence to output light of the different primary colors from the light guide consecutively in a time of less than 4 milliseconds during the frame of the video signal, and to output no light during the remainder of the frame,

and operating the pixels to modulate the light of each primary color output from the light guide in at least one of intensity and pulse width.

12. The method of claim 11, wherein the light guide has a light input edge that receives light of the different primary colors and propagates the light in the light guide by total internal reflection.

13. The method of claim 11 further comprising:

generating gray scale.

14. The method of claim 13, wherein the generating comprises modulating the width of a light pulse.

15. The method of claim 13, wherein the generating comprises modulating the intensity of the light.

16. The method of claim 11 further comprising:

outputting the light of the different primary colors at fixed intervals regardless of program content.

17. The method of claim 11 further comprising:

independently controlling the light of the different primary colors.

18. The method of claim 17 further comprising:

asynchronously outputting the light of the different primary colors during the frame according to program content.

19. The method of claim 11 further comprising:

increasing an intensity of the light by a ratio of 1/n, wherein n is equal to a number of different primary colors output by the light guide.